If you have a standard rowing stroke, back muscles are far more utilized in rowing than cycling. Some quotes from the first paper I found in a Google search (https://www.researchgate.net/profile/Niels-Secher-3/publication/14772252_Physiological_and_Biomechanical_Aspects_of_Rowing/links/5638b1da08ae4bde5021d3fb/Physiological-and-Biomechanical-Aspects-of-Rowing.pdf ) are below.
"First, in contrast to cycling and running, almost every muscle group takes an active part in rowing. Blood variables change to the extreme during ‘all-out’
rowing because of the workload of the arm, back and leg muscles. ""Surface electrodes have been used to record muscle activity during rowing (Ishiko 1968). Especially high muscle activity was noted in biceps and triceps brachia and latissimus dorsi. "
However, lower back issues are fairly common with cycling, which I expect you are referring to. Cycling back issues more often relate to posture and strain on lower back from the position maintained while cycling, rather than high utilization of back muscles. It’s more of an issue for outdoor cycling than cycling on stationary bike. There are recumbent bike options for persons who have lower back issues that avoid this position.